GENEVA -- Atheists and other religious skeptics suffer persecution or discrimination in many parts of the world and in at least seven countries can be executed if their beliefs become known, according to a report issued Monday.

The study, from the International Humanist and Ethical Union (IHEU), showed that "unbelievers" in Islamic countries face the most severe -- sometimes brutal -- treatment at the hands of the state and adherents of the official religion.

But it also points to policies in some European countries and the United States that favor the religious and their organizations and treat atheists and humanists as outsiders.

The report, "Freedom of Thought 2012," said "there are laws that deny atheists' right to exist, curtail their freedom of belief and expression, revoke their right to citizenship, restrict their right to marry."

Other laws "obstruct their access to public education, prohibit them from holding public office, prevent them from working for the state, criminalize their criticism of religion, and execute them for leaving the religion of their parents."

In the United States, for example, where freedom of religion and speech is protected, a social and political climate prevails "in which atheists and the non-religious are made to feel like lesser Americans, or non-Americans," the report said.

In at least seven U.S. states, constitutional provisions are in place that bar atheists from public office and one state, Arkansas, has a law that bars atheists from testifying as witnesses at trials, the report said.

"It is often not the case that when people hear of freedom of religion they interpret that in terms of the non-religious too," Bob Churchill, a spokesperson for IHEU, told NBC News. "This report shows clearly how people who mildly criticize religion may go on to suffer months or years in jail, even awaiting a death sentence."

The report was welcomed by Heiner Bielefeldt, U.N. special rapporteur on freedom of religion or belief, who said in a brief introduction there was little awareness that atheists were covered by global human rights agreements.

The IHEU -- which links more than 120 humanist, atheist and secular organizations in more than 40 countries -- said it was issuing the report to mark the U.N.'s Human Rights Day on Monday.

According to its survey of some 60 countries, the seven where expression of atheist views or defection from the official religion can bring capital punishment are Afghanistan, Iran, Maldives, Mauritania, Pakistan, Saudi Arabia and Sudan.

Forced to lieThe 70-page report lists no recent cases of actual execution for "atheism" -- but researchers say the offence is often subsumed into other charges.

In a range of other countries -- such as Bangladesh, Egypt, Indonesia, Kuwait and Jordan -- publication of atheist or humanist views on religion are totally banned or strictly limited under laws prohibiting "blasphemy."

In many of these countries, and others like Malaysia, citizens have to register as adherents of a small number officially-recognized religions -- which normally include no more than Christianity and Judaism as well as Islam.

Atheists and humanists are thereby forced to lie to obtain their official documents without which it is impossible to go to university, receive medical treatment, travel abroad or drive.

In Europe, sub-Saharan Africa and Latin and North America, countries which identify themselves as secular give privileges to or favor Christian churches in providing education and other public services, the IHEU said.

In Greece and Russia, the Orthodox Church is fiercely protected from criticism and is given pride of place on state occasions, while in Britain bishops of the Church of England have automatic seats in the upper house of parliament.